The present invention is directed, in general, to power electronics and, more specifically, to an integrated controller, method of operation thereof and a power supply employing the same.
The electronics industry continues to develop smaller equipment that performs more functions, which in turn may require increasingly more power from smaller, more compact power supplies. Additionally, such a power supply may also have internal bias supply requirements for additional voltages that are usually different from the main power supply voltages. Bias supplies are used in power supplies to provide operating voltages needed by internal power control circuits or other circuits that provide a proper operation during start-up or sustained power supply operation. The bias supply voltages and power requirements provided by the bias supplies typically add another level of complexity to an already demanding environment.
A safety requirement to isolate various portions of a power supply, such as an input section from an output section, represents one of these levels of complexity to both the generation and use of bias supply voltages associated with the bias supplies. A conventional approach to providing appropriately isolated bias supply voltages is to use one or more independent or separate bias supplies to provide the bias voltages needed. However, independent bias supplies tend to reduce overall efficiency and to increase both costs and size of a power supply. Unfortunately, users are demanding increased efficiency, reduced costs and smaller sizes, which are attributes contrary to the employment of independent bias supplies and therefore, make them somewhat unattractive.
The operational requirements of semiconductor devices that employ power supplies have also continued to escalate. This is especially true with regard to transient power supply situations that affect power supply output voltage characteristics. Conventional, non-independent bias supply solutions often suffer from start-up characteristics that produce inflection points in an output voltage characteristic. One such characteristic may be a voltage that first rises, then falls and finally rises again while always remaining positive. Many semiconductor devices, subjected to such an output voltage characteristic, will latch-up or otherwise become inoperative thereby making such a voltage characteristic unacceptable.
Accordingly, what is needed in the art is a way to provide a power supply output voltage that increases smoothly during start-up and other situations without employing independent bias supplies.
To address the above-discussed deficiencies of the prior art, the present invention provides an integrated controller for use with a power supply employing a pulse width modulator. In one embodiment, the integrated controller includes a primary control circuit configured to provide a control signal to the pulse width modulator. Additionally, the integrated controller includes a feedback circuit configured to monitor an output signal of the pulse width modulator and to modify the control signal thereby enabling a substantially monotonic increase in an output voltage of the power supply during a non-steady state period of operation thereof.
In another aspect, the present invention provides a method of operating a power supply employing a pulse width modulator. In one embodiment, the method includes providing a control signal to the pulse width modulator. The method also includes monitoring an output signal of the pulse width modulator, and modifying the control signal to enable a substantially monotonic increase in an output voltage of the power supply during a non-steady state period of operation thereof.
The present invention also provides, in yet another aspect, a power supply employing a power stage that provides an output voltage and a pulse width modulator that provides an output signal to a power switch of the power stage. The power supply also employs an integrated controller that includes a primary control circuit that provides a control signal to the pulse width modulator, and a feedback circuit that monitors the output signal of the pulse width modulator and modifies the control signal to enable a substantially monotonic increase in the output voltage during a non-steady state period of operation of the power supply. Additionally, the power supply further employs a secondary control circuit that is coupled to an output of the power supply and coupled to the integrated controller.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.